Reconstituted tobacco composition and finished products are well-known. They are commonly prepared from comminuted tobacco material which may include leaf, stem, or dust in a composition which includes an adhesive substance (sometimes a tobacco ingredient itself such as tobacco pectin) which renders the composition cohesive upon treatment. Aqueous slurries have often been employed from which cast films are prepared and thereafter dried. As this involves substantial expense for the drying step, other direction have been considered. Thus, U.S. Pat. Nos. 2,708,175 and 2,845,933 describe compositions of dry tobacco and a mucilaginous plant gum at low moisture level which are worked by a mechanical shearing action as provided by closely spaced steel rollers. U.S. Pat. No. 3,098,492 utilizes ungelatinized starch and hot extrusion. U.S. Pat. Nos. 3,166,078 and 3,209,763 employ rollers or a progressively contracting tube to accomplish sheet formation at low moisture. Ultrasonic homogenizers or disc refiners are used to process the tobacco in U.S. Pat. Nos. 3,141,462 and 3,467,109. Grunwald et al. in U.S. Pat. No. 3,424,170 uses high pressure rollers. The manufacture of reconstituted tobacco sheet products of relatively high density (0.6-0.8g/cc relative to natural tobacco leaf at about 0.4g/cc) via plastics technology was described by H. Merritt (U.S. Pat. No. 3,012,562.)
It is also known to produce reduced density tobacco compositions as by use of blowing agents, fluorinated materials, and the like. The smoking articles produced from these compositions are of value for improved filling power and, where desired, reduced delivery of smoke tars or other smoke components.
In U.S. Pat. No. 3,364,935, U.S. Pat. No. 3,404,690, U.S. Pat. No. 3,404,691 and U.S. Pat. No. 3,410,279, Moshy and Germino described inventions to produce a foamed tobacco slurry which, when cast or otherwise formed into a desired shape and suitably treated will provide a smoking article with an open cellular structure. The Moshy and Germino inventions involve processes for combining a foaming agent, a foam-stabilizing agent and tobacco, at least one element of said mixture being adhesive, creating a tobacco foam slurry from said mixture, forming said slurry into a predetermined shape and drying said shaped slurry to a preselected moisture content to produce a stable foamed product in which tobacco particles are spaced from each other by a gaseous medium. During the process of pumping and shaping the foamed tobacco slurry, the work done on this slurry can cause some degree of foam breaking and collapse. Furthermore, during the process of drying the shaped foamed tobacco slurry, further foam disruption and collapse can occur. Although the practice of the Moshy and Germino patents does result in foamed tobacco products, the inability to obtain optimum foam stabilization characteristics when using the foamstabilizing ingredients specified make the production of foamed tobacco products with exact density characteristics difficult to obtain and control. Since the uniformity of weight, firmness and draw of smoking articles produced by this process depends on control of the ultimate foam density characteristics, it is apparent to those skilled in the art that a significantly more stable foamed tobacco slurry is desired to provide the degree of foam density control during transfer, shaping and drying which is necessary for a commerically acceptable process and product.
Accordingly, it was the object of Monte in U.S. Pat. No. 3,613,693 to provide for an improved foam reconstituted product and an improved process for making same to exacting and reproducible density specifications. Nevertheless, because the process still involves the use of foamed slurries, the process is still not without disadvantages. For example, the drying rates for such slurries are extremely low compared to unfoamed slurries and they are still subject to some degree of foam collapse due to the method(s) of heat application during drying.
Based upon such background, initial experimentation with tobacco/binder systems in extruder equipment to produce controlled and reduced density reconstituted products was carried out. It was first discovered that such systems are remarkably non-homogeneous, and heavily dependent upon tobacco dimension and the presence of water to permit regular feeding through a conventional plastic extruder. Neither the presence of moisture nor the use of conventional blowing agents was successful in effecting a controlled reduction of density.